Balloon catheters are used to perform various medical procedures wherein the balloon is positioned within a body lumen or canal and subsequently inflated. In some of these medical procedures, such as in an angioplasty procedure, the balloon is inflated so as to expand the interior volume of the body canal. In this type of procedure, the balloon is expanded to apply pressure to the interior surface of the body canal to thereby compress any tissue protruding into the canal and thereby enlarge the interior volume thereof. Once the tissue has been compressed, and the body canal widened, the balloon is deflated and removed.
In other types of medical procedures, such as photodynamic therapy (PDT), a balloon catheter is used to align and stabilize the catheter within the body lumen. For example, the balloon catheter may be inflated under low pressure within a body lumen such as the esophagus. A therapeutic fiber optic device is then inserted into the catheter in the vicinity of the balloon. The therapeutic fiber optic device is then used to emit light waves to treat the surrounding tissue. In this procedure, the balloon is used to both align the catheter in the center of the body lumen, and to prevent the catheter from moving during the PDT procedure. However, the tissue to be treated must not be unduly compressed by the expanded balloon. Thus, the balloon is expanded only enough to lightly contact the interior surface of the lumen and align the catheter.
As will be explained below, conventional balloon catheters have a number of shortcomings that make them inadequate for many of the above-described procedures, and in particular, for PDT procedures.
A typical balloon catheter 10 is shown in FIGS. 1A-1D. As best seen in FIG. 1A, a conventional balloon catheter 10 comprises a balloon 12 that is affixed to a catheter 14. The balloon 12 is typically manufactured from a non-elastomeric material (e.g., a semi-rigid or non-compliant material), and includes a distal neck or end 16, a proximal neck or end 18 and a central portion 20. The balloon 12 is affixed to the catheter 14 by inserting the distal end 22 of the catheter 14 into and through the proximal end 18 of the balloon 12. The balloon 12 is then slid over the catheter 14 until the distal end 22 of the catheter 14 is inserted into the distal end 16 of the balloon 12. The distal end 22 of the catheter 14 is then affixed to the distal end 16 of the balloon 12 by an adhesive, ultrasonic welding, or some other method. The proximal end 18 of the balloon 12 is similarly affixed to the outer wall of the catheter 14 so as to anchor and seal the proximal end of the balloon 12.
The catheter 14 includes an aperture 24 for the introduction of air or some other fluid into the interior volume of the balloon 12. Although not shown in the drawings, the proximal end of the catheter 14 is typically attached to a device, such as a syringe, that is manipulated to either inflate or deflate the balloon 12 by injecting a fluid into or withdrawing a fluid from, respectively, the interior volume of the balloon 12.
The conventional balloon catheter 10 has a number of drawbacks for use in many of the above-described procedures, and in particular, for use in PDT procedures. When initially manufactured, the balloon catheter 10 generally assumes a shape and configuration as depicted in FIG. 1A. As can be seen in this drawing, the central portion 20 of the balloon 12 is connected to the distal end 16 and the proximal end 18 by tapered or conical sections 26. The tapered sections 26 provide a transition between the larger diameter of the central portion 20 of the balloon 12 and the smaller end portions of the balloon 12 (i.e., the distal end 16 and the proximal end 18) that are connected to the catheter 14.
At the time of packaging by the manufacturer or at the initiation of the medical procedure, the balloon 12 is typically deflated prior to inserting of the balloon catheter 10 into the body canal. Deflation of the balloon 12 is necessary to reduce the overall cross-section or diameter of the device to permit it to pass through an endoscope and/or to navigate and pass through the body's internal canals. FIG. 1B depicts the balloon catheter 10 in the deflated state. As can be seen in this drawing, the balloon 12 is forced to compress in length. This is because the overall length of the material that forms the central portion 20 and the tapered portions 26, as measured along the surface of the balloon 12 in a generally axial direction of the catheter 14 (i.e., from one end of the balloon 12 to the other), is greater than the distance between the distal end 16 and the proximal end 18. As a result of this compression, transverse creases 28 typically form along the surface of the balloon 12.
After the balloon catheter 10 is positioned within the body canal (not shown) at the desired location, inflation of the balloon 12 is initiated as shown in FIG. 1C. As depicted in this drawing, the creases 28 in the surface of the material may prevent the balloon 12 from fully expanding to its normal length (i.e., as shown in FIG. 1A). In other words, the balloon 12 tends to act like a spring under tension. As a result, the portion of the catheter 14 that lies between the distal end 16 and the proximal end 18 of the balloon 12 will be forced into compression, and may begin to bow 30 as a result of these compressive forces.
As inflation of the balloon 12 continues, bowing 30 of the catheter 14 may be increased as shown in FIG. 1D. This is the result of transverse or outward expansion of the central portion 20 of the balloon, which tends to pull the distal end 16 and the proximal end 18 towards each other.
Bowing 30 of the catheter 14 may not be eliminated unless and until a sufficiently high inflation pressure is applied to the balloon 12 (see FIG. 1A). However, some bowing 30 of the catheter 14 may nevertheless remain if the initial deflation of the balloon 12 (see FIG. 1B) resulted in the formation of permanent transverse creases 28. Permanent bowing 30 of the catheter 14 is more likely if the balloon 12 is constructed from a non-elastomeric material.
The formation of transverse creases 28 and the bowing 30 of the catheter 14 can negatively impact the use of the conventional balloon catheter 10 during certain medical procedures. For example, during angioplasty procedures, permanent creases 28 in the surface of the balloon 12 may prevent the complete or uniform compression of the tissue on the interior surface of the body canal against which the balloon 12 is expanded. This may result in a decrease in effectiveness of the angioplasty procedure.
With respect to PDT procedures, any bowing 30 of the catheter 14 can prevent accurate alignment and centering of the catheter 14 within the body lumen or canal to be treated. This is because typical PDT procedures do not allow the expanded balloon 12 to exert excess pressure or heavy contact on the interior surface of the body lumen. Thus, the balloon 12 cannot be inflated with a pressure that is sufficient to eliminate any bowing 30 of the catheter 14. The catheter 14 may consequently not be properly centered in the body lumen. As a result, effective treatment of the body lumen tissue with the therapeutic fiber optic device, which is positioned inside the catheter 14, may be inhibited.
In addition, because the distal end 16 and the proximal end 18 of the balloon 12 are both fixed to the catheter 14 at permanent (i.e., non-moveable) locations, the ability to reduce the diameter of the deflated balloon 12 may be limited, particularly if the balloon 12 is manufactured from a non-elastomeric material. In other words, the central portion 20 of the balloon 12 may not compress tightly about the catheter 14 during deflation because of the creases 28 formed in the material of the balloon 12 (see FIG. 1B). Bunching of the balloon material may likewise limit the deflated diameter or cross-section of the balloon 12. Consequently, the device may be more difficult to maneuver during ingress or egress of the device through the body's canals. In addition, the resulting “wrinkled” surface of the balloon 12 may cause irritation to body canal tissue during ingress or egress of the device and/or prevent the device from passing through the endoscope channel.
To overcome one or more of the above-described problems and disadvantages of conventional balloon catheters, an improved balloon catheter has been developed that includes a balloon that is fixedly connected to the catheter at only a single location. An example of the improved balloon catheter 40 is shown in FIG. 2, which illustrates the distal portion of the improved balloon catheter. The balloon catheter 40 includes a rounded or cylindrically shaped balloon 42 that is affixed to a catheter 44. In particular, the proximal end 46 of the balloon 42 is fixedly connected to the distal end 48 of the catheter 44. A tapered stiffening member 50 extends distally from the distal end 48 of the catheter 44 and through the interior of the balloon 42. The distal end 52 of the stiffening member 50 forms a slip joint connection 54 with the distal end 56 of the balloon 42. The slip joint 54 allows the distal end 56 of the balloon 42 to axially move or translate with respect to the distal end 48 of the catheter 44 while maintaining axial alignment of the balloon 42 relative to the stiffening member.
The slip joint 54 allows the overall length of the balloon 42 to change during inflation or deflation. In addition, the slip joint 54 prevents the relative axial rigidity of the catheter 44 and stiffening member 50 from generating any axial tensile or compressive forces in the balloon 42. Consequently, transverse creasing of the central portion of the balloon 42 is eliminated or at least minimized. The slip joint 54 similarly prevents the balloon 42 from generating any adverse forces in the catheter 44 or stiffening member 50 during inflation or deflation of the device. Thus, the catheter 44 and stiffening member 50 will not be bowed or stretched as result of the inflation or deflation of the balloon 42. Moreover, the central portion of the balloon 42 can generally be collapsed into a smaller diameter or cross-section for ingress or egress of the balloon catheter 40 through the body's canals and/or the endoscope channel.
Although slip joint balloon catheters have overcome many of the disadvantages of conventional fixed length balloon catheters, slip joint balloon catheters may be difficult to refold into the pre-inflated folded state. For example, many semi-rigid balloon catheters are initially folded to have three or more “wings” so as to minimize the cross-sectional area and transverse creasing of the deflated balloon for delivery to the target site within the patient. After the balloon has been inflated (e.g., to perform the medical procedure), the balloon must then be deflated so that it can be removed from the patient. However, the balloon, and particularly a slip joint balloon, may not refold into the initial folded configuration. For example, the balloon may only fold into a 2-wing configuration, or may bunch up in response to the negative pressure used to deflate the balloon. This is most likely due to elongation and/or plastic deformation of the balloon during inflation. As a result, the balloon may not deflate back into the same cross-sectional area as that of the initially folded balloon. This may make it difficult or impossible to remove the balloon from the patient, particularly if the balloon catheter was introduced into the patient through an endoscope or other elongate introducer. The balloon may also get jammed in the endoscope upon withdrawal. These problems can be exacerbated with semi-rigid stageable balloons that are designed to undergo plastic deformation (permanent stretching) during inflation in order to achieve various discrete diameters at specified corresponding pressures. This is most likely due to the loss of “fold memory” in the balloon material as a result of the plastic deformation incurred by the inflation of the balloon.
What is needed is an improved slip joint balloon catheter that overcomes the disadvantages of conventional devices. In particular, what is needed is a slip joint balloon catheter that can be deflated to a minimal diameter for ingress and egress through the body's canals and/or an endoscope channel, that resists the formation of transverse creases in the surface of the balloon during deflation, and that assumes a predetermined and desired folding configuration upon deflation.